Fix formatting of the release CHANGELOG file 

- Add backquotes around the changelog
- Add empty line at the end of the changelog
- Enforce the use of the master changelog prior to release

Fixes #2281.

--
Change-Id: I449f5209a6b05e65411a64ce82ea1d89d60ee4d3
Reviewed-on: https://cr.bazel.build/8044
PiperOrigin-RevId: 144080940
MOS_MIGRATED_REVID=144080940
diff --git a/scripts/release/common.sh b/scripts/release/common.sh
index 5f83af7..7cea006 100755
--- a/scripts/release/common.sh
+++ b/scripts/release/common.sh
@@ -196,19 +196,30 @@
 
 # Generate the release message to be added to the changelog
 # from the release notes for release $1
+# Args:
+#   $1: release name
+#   $2: release ref (default HEAD)
+#   $3: delimiter around the revision information (default none)
 function generate_release_message() {
   local release_name="$1"
   local branch="${2:-HEAD}"
+  local delimiter="${3-}"
   local baseline="$(get_release_baseline "${branch}")"
   local cherrypicks="$(get_cherrypicks "${branch}" "${baseline}")"
 
-cat <<EOF
-$(get_release_title "$release_name")
+  get_release_title "$release_name"
+  echo
 
-$(create_revision_information $baseline $cherrypicks)
+  if [ -n "${delimiter}" ]; then
+    echo "${delimiter}"
+  fi
+  create_revision_information $baseline $cherrypicks
+  if [ -n "${delimiter}" ]; then
+    echo "${delimiter}"
+  fi
 
-$(get_release_notes "${branch}")
-EOF
+  echo
+  get_release_notes "${branch}"
 }
 
 # Returns the release notes for the CHANGELOG.md taken from either from